java - 如何将 ListView 保存为文本文档而不是将其加载回程序中

Question

我目前正在制作一个程序，您可以在其中使用Java从 ListView 中添加和删除项目，我希望它能够在您向 ListView 添加项目和删除项目时自动保存。我很难弄清楚如何做到这一点，任何帮助将不胜感激。我对编程还很陌生，并且仍在尝试弄清楚这一切，这是我到目前为止的代码。

import java.io.File;
import java.io.IOException;
import java.io.PrintWriter;

import javafx.application.*;
import javafx.collections.FXCollections;
import javafx.collections.ObservableList;
import javafx.event.ActionEvent;
import javafx.event.EventHandler;
import javafx.geometry.Insets;
import javafx.geometry.Pos;
import javafx.scene.Scene;
import javafx.scene.control.Button;
import javafx.scene.control.Label;
import javafx.scene.control.ListView;
import javafx.scene.control.TextField;
import javafx.scene.layout.BorderPane;
import javafx.scene.layout.GridPane;
import javafx.scene.layout.HBox;
import javafx.scene.layout.Priority;
import javafx.scene.layout.VBox;
import javafx.scene.text.Font;
import javafx.scene.text.FontWeight;
import javafx.stage.Stage;



public class LendingLibraryGUI extends Application {
    LendingLibrary LendingLibrary = new LendingLibrary(); //Creating an Object to access total numbers of items
    MediaItems Media = new MediaItems(); // creating an array of object to access MediaItems class and allowing it to hold 100 items 
    private ListView<String> library = new ListView<String>();
    ObservableList<String> libraryList = FXCollections.<String>observableArrayList("yes","no");

    @Override
    public void start(Stage primaryStage) throws Exception {
        BorderPane display = new BorderPane(); //Main display
        GridPane buttons = new GridPane(); //location to display buttons
        TextField outPut = new TextField(); //Text field to show inventory
        Insets padding = new Insets(10); //creates Insets for padding
        buttons.setPadding(padding); //padding around grid pane
        buttons.setHgap(10); //Horizontal gap
        library.setItems(libraryList);



        for (int i =0; i !=4;i++) { //Loop to create Buttons
            String[] actionButtons = {"Add","Check Out","Check In","Delete"};//String to store Button names
            Button temp = new Button(actionButtons[i]);
            temp.setMaxSize(Double.MAX_VALUE, Double.MAX_VALUE);
            buttons.add(temp, i, 0); //add buttons to grid pane
            GridPane.setHgrow(temp, Priority.ALWAYS);
            GridPane.setVgrow(temp, Priority.ALWAYS);
            if (temp.getText().equals("Add")) {
                temp.setOnAction((e) -> add());
            }
            else if (temp.getText().equals("Delete")) {

                temp.setOnAction((e) -> deleteLibrary());

            }
        }


        outPut.setEditable(false); //no editing
        outPut.setFont(Font.font("monospace", FontWeight.BOLD, 20));
        outPut.setMinHeight(300);//sets minimum height
        display.setTop(library); //sets output in display on top
        display.setCenter(buttons); //sets buttons on center 


        Scene scene = new Scene(display); //creates new scene
        primaryStage.setTitle("Lending Library"); //sets title of GUI
        primaryStage.setScene(scene); //adds scene to GUI
        primaryStage.setMinHeight(400); //Minimum height
        primaryStage.setMinWidth(350);//Minimum Width
        primaryStage.show();//Displays GUI to user
    }

    public static void main(String[] args) {

        launch(args);

    }


    private void add() {
        inputGUI("Title:");
    }

    private void inputGUI(String input) {
        Stage secondaryStage = new Stage();
        BorderPane border = new BorderPane();
        VBox titlePane = new VBox(8);
        HBox buttonLayout = new HBox(8);
        Label lblTitle = new Label(input);
        Button save = new Button("Save");
        Button close = new Button("Close");
        Insets padding = new Insets(10);
        TextField txt = new TextField("");
        close.setOnAction((e) -> secondaryStage.close());;



        save.setOnAction(new EventHandler<ActionEvent>() {
            @Override
            public void handle(ActionEvent e) {
                try {

                    LendingLibrary.save(library);
                } catch (IOException e1) {
                    e1.printStackTrace();
                }

                if (txt.getText().trim().isEmpty()) {

                }
                else {

                    if (input.equals("Title:")) {
                        Media.setTitle(txt.getText());
                        secondaryStage.close();
                        inputGUI("Format:");
                    }
                    else if (input.equals("Format:")) {
                        Media.setFormat(txt.getText());
                        secondaryStage.close();
                        addToLibrary();
                    }
                    else if (input.equals("Who did you loan this to?")) {



                    }
                    else if (input.equals("When did you loan it(date)?")) {


                    }
                }

            }
        });

        buttonLayout.getChildren().addAll(close,save);
        titlePane.setPadding(padding);
        titlePane.getChildren().addAll(lblTitle,txt,buttonLayout);
        border.setCenter(titlePane);
        BorderPane.setAlignment(titlePane, Pos.CENTER);

        Scene scene = new Scene(border); //creates new scene
        secondaryStage.setTitle("Input"); //sets title of GUI
        secondaryStage.setScene(scene); //adds scene to GUI
        secondaryStage.setMinHeight(200); //Minimum height
        secondaryStage.setMinWidth(350);//Minimum Width
        secondaryStage.show();//Displays GUI to user


    }


    private void addToLibrary() {
        String total;
        total = Media.getTitle();
        total = total + " ("+ Media.getFormat() +")";
        libraryList.add(total);
        library.setItems(libraryList);



    }

    private void deleteLibrary() {
        int selectedItem = library.getSelectionModel().getSelectedIndex();
        libraryList.remove(selectedItem);
    }

    private void checkOut() {

    }

}

任何其他指示或建议将不胜感激!

提前致谢

编辑:再说一次，我很新，只是想学习基本的东西，这不是我要继续阅读一本书的东西，这是它试图教我的东西。

public void save(ListView<String> library) throws IOException {
    File file = new File ("LendingLibrary.txt"); //creates text file
    PrintWriter output = new PrintWriter(file);

    if(file.exists()) { //if the file exists
        output.println(library);
        output.close();

    }

    if(!file.exists()) { //if file doesn't exist
        System.out.println("Error creating file");
    }



}

Answer 1

您真正感兴趣的是保存 ListView 显示的数据，您不需要所有其他布局信息和内容，因为它们在应用程序中静态定义并在每次运行时自动加载。

现在，虽然将数据保存在文件中并在每次需要时加载它可以工作，但这通常不是最好的。更好的方法是使用数据库以关系实体的形式存储应用程序的数据，这样您就可以使用更安全、更一致的方法。要开始进入该主题，您可以继续咨询官方reference 。

如果您想首先尝试使用文件方法，建议是以某种结构化格式保存数据，这样可以轻松保存和加载，或者更准确地说序列化/反序列化。为此，您可以使用 json 格式将数据存储在文件中，并且可以使用 gson库例如:

1. ListView 的每一行都是一个包含数据的对象。
2. 阅读:使用 gson 将数据列表序列化为 json 格式，并将每个数据存储在单独的行中。
3. 阅读:加载字符串列表并使用 gson 将它们反序列化为 java 类。